The impact of temperature on the performance of anaerobic biological treatment of perchlorate in drinking water

A 20-month pilot-scale study was conducted to examine the impact of temperature on the performance of an anaerobic biological contactor used to treat perchlorate-contaminated water. The contactor was successfully acclimated with indigenous microorganisms. Influent temperatures varied from 1.4 to 30 °C. The objectives of the study were to investigate the effects of temperature on perchlorate removal, nitrate removal, nitrite formation, dissolved oxygen consumption, sulfide production, and nutrient acetate consumption. The results confirmed that consistent biological perchlorate removal to 2 μg/L is feasible at temperatures above 10 °C. Effluent concentrations of perchlorate, nitrate, and dissolved oxygen varied inversely with temperature, while sulfide varied positively with temperature. Under the conditions that prevailed during this study, 10 °C was a threshold temperature below which microbial activity, including perchlorate reduction, decreased dramatically.     

Biodegradation of petroleum hydrocarbons in an immobilized cell airlift bioreactor

An "immobilized cell airlift bioreactor", was used for the aerobic bioremediation of simulated diesel fuel contaminated groundwater and tested with p-xylene and naphthalene in batch and continuous regimes. The innovative design of the experiments consists of two stages. At the first stage "immobilized soil bioreactor" (ISBR) was used to develop an efficient microbial consortium from the indigenous microorganisms, which exist in diesel fuel contaminated soil. The concept of ISBR relies on the entrapment of the soil particles into the pores of a semi-permeable membrane, which divides the bioreactor into two aerated and non-aerated portions. The second stage involves inoculating the "immobilized cell air lift bioreactor" with the cultivated microbial consortia of the first stage. Immobilized cell airlift bioreactor has the same configuration as ISBR except that in this bioreactor instead of soil, microorganisms were immobilized on the fibers of the membrane. The performance of a 0.83 L immobilized cell airlift bioreactor was investigated at various retention time (0.5-6 h) and concentrations of p-xylene (15, 40 and 77 mg/L) and naphthalene (8, 15 and 22 mg/L) in the continuous operation. In the batch regime, 0.9L bioreactor was operated at various biodegradation times (15-135 min) and concentrations of p-xylene (13.6, 44.9 and 67.5 mg/L) and naphthalene (1.5 and 3.8 mg/L). Under the conditions of the complete biodegradation of p-xylene and naphthalene, the obtained volumetric biodegradation rates at biomass density of 720 mg/L were 15 and 16 mg/L h, respectively.     

除蚤剂对活性炭上微生物的影响

从对生物量和微生物耗氧速率的影响方面，考察了盐水、氨水、氯和氯胺等四种除蚤剂对活性炭上微生物的影响。小试结果表明，投加4种药剂虽使得活性炭上的生物量降低1～2个数量级，但基本上能维持在10^6数量级，即这种影响在可接受的范围之内；药剂对活性炭上微生物的活性具有抑制作用。选取盐水和氨水做对活性炭上微生物影响的生产性试验，结果表明：投加20g／L的盐水和10mg／L的氨水后，活性炭上的生物量降低了40％～60％，但都能维持在10^6数量级，因此认为药剂对活性炭上生物量的影响可以忽略不计；同时，微生物的活性随着过滤的进行而逐渐得到恢复，用盐水浸泡过的滤池需要5d的恢复时间，而用氨水浸泡的滤池只需2～3d。可见，采用盐水或氨水浸泡活性炭滤池来控制剑水蚤的生长是可行的。     

Potential for activated persulfate degradation of BTEX contamination

The present study focused on evaluation of activated persulfate (PS) anion (S(2)O(8)(2-)) oxidative degradation of benzene, toluene, ethylbenzene, and xylene (constituents of gasoline and known collectively as BTEX) contamination. The results indicated that BTEX were effectively oxidized by PS in aqueous and soil slurry systems at 20 degrees C. PS can be activated thermally, or chemically activated with Fe(2+) to form the sulfate radical (SO(4)(-)) with a redox potential of 2.4V. The degradation rate constants of BTEX were found to increase with increased persulfate concentrations. For two PS/BTEX molar ratios of 20/1 and 100/1 experiments, the observed aqueous phase BTEX degradation half-lives ranged from 3.0 to 23.1 days and 1.5 to 20.3 days in aqueous and soil slurry systems, respectively. In the interest of accelerating contaminant degradation, Fe(2+) and chelated Fe(2+) activated persulfate oxidations were investigated. For all iron activation experiments, BTEX and persulfate degradations appear to occur almost instantaneously and result in partial BTEX removals. It is speculated that the incomplete degradation reaction may be due to the cannibalization of SO(4)(-) in the presence of excess Fe(2+). Furthermore, the effects of various chelating agents including, hydroxylpropyl-beta-cyclodextrin (HPCD), ethylenediaminetetraacetic acid (EDTA), and citric acid (CA) on maintaining available Fe(2+) and activating PS for the degradation of benzene were studied. The results indicated that HPCD and EDTA may be less susceptible to chelated Fe(2+). In contrast, CA is a more suitable chelating agent in the iron activated persulfate system and with a PS/CA/Fe(2+)/B molar ratio of 20/5/5/1 benzene can be completely degraded within a 70-min period.     

驯化耐盐活性污泥处理高盐度工业废水

以某石化企业废水处理厂纯氧曝气池剩余污泥为接种污泥,采用逐步提高盐度负荷的方法对活性污泥进行耐盐性驯化,考察了驯化效果.结果表明,经过较长时间的驯化,活性污泥微生物能够适应高盐度的生存环境并能在其中生长、繁殖.驯化后的活性污泥能较好地抵御高盐度冲击负荷.在进水TDS为18～35 g/L的条件下,驯化后的活性污泥纯氧曝气池对高盐度工业废水中COD的平均去除率为85.7%,比原废水处理厂常规活性污泥纯氧曝气池的高出近10%.该驯化方法可以驯化出能耐受较高盐浓度并具有良好COD降解性能的耐盐活性污泥.     

异养硝化菌强化饱和基质材料降解水体氨氮的研究

将优势菌技术运用于饱和基质材料中,考察基质材料对水中氨氮的吸附特性以及微生物原位强化饱和基质材料后对氨氮的降解效果。试验结果表明,沸石对氨氮的吸附量高于活性炭。对氨氮含量为110mg／L的模拟富营养化水体进行360h动态吸附后,沸石和活性炭吸附后出水中氨氮平均含量分别为73．3l和89．18mg／L,沸石显示出作为基质材料的优越性。对饱和基质材料进行异养硝化茵强化96h后,沸石柱和活性炭柱出水氨氮平均含量分别降低8．58和17．31mg／L,并且活性炭和沸石表面形成稳定的生物膜。因此,对富营养水体在基质吸附基础上进行微生物降解的方法是可行的。     

PAC/PS预处理对水中镉的去除及UF膜污染控制

采用粉末活性炭耦合过硫酸盐(PAC/PS)作为超滤的预处理工艺,考察其对原水中镉和天然有机物的去除效果,以及对超滤膜污染控制的影响。结果表明,对于镉超标6倍的原水水样,当PAC和PS投加量分别为30 mg/L和300μmol/L、接触时间为60 min时,UV₂₅₄、DOC和镉的去除率分别可达到91.7%、68.2%和92.7%,镉浓度可降至《生活饮用水卫生标准》(GB 5749—2006)规定的限值(5μg/L)以下;与直接超滤相比,设置PAC/PS预处理工艺后超滤膜比通量提升了50.5%,XDLVO预测模型中胶体污染物-超滤膜相互作用的总界面能降低了75.38%,超滤膜污染减轻。     

Simultaneous adsorption and biodegradation processes in sequencing batch reactor (SBR) for treating copper and cadmium-containing wastewater

The application of simultaneous adsorption and biodegradation processes in the same reactor is known to be effective in the removal of both biodegradable and non-biodegradable contaminants in various kinds of wastewater. The objective of this study is to evaluate the efficacy of the two processes under sequencing batch reactor (SBR) operation in treating copper and cadmium-containing synthetic wastewater with powdered activated carbon (PAC) as the adsorbent. The SBR systems were operated with FILL, REACT, SETTLE, DRAW and IDLE periods in the ratio of 0.5: 3.5: 1.0: 0.75 :0.25 for a cycle time of 6 h. In the presence of 10 mg/L Cu(II) and 30 mg/L Cd(II), respectively, the average COD removal efficiencies were above 85% with the PAC dosage in the influent solution at 143 mg/L compared to around 60% without PAC addition. Copper(II) was found to exert a more pronounced inhibitory effect on the bioactivity of the microorganisms compared to Cd(II). It was observed that the combined presence of Cu(II) and Cd(II) did not exert synergistic effects on the microorganisms. Kinetic study conducted for the REACT period showed that the addition of PAC had minimized the inhibitory effect of the heavy metals on the bioactivity of microorganisms.     

Effect of electrokinetic remediation on indigenous microbial activity and community within diesel contaminated soil

Electrokinetic remediation has been successfully used to remove organic contaminants and heavy metals within soil. The electrokinetic process changes basic soil properties, but little is known about the impact of this remediation technology on indigenous soil microbial activities. This study reports on the effects of electrokinetic remediation on indigenous microbial activity and community within diesel contaminated soil. The main removal mechanism of diesel was electroosmosis and most of the bacteria were transported by electroosmosis. After 25 days of electrokinetic remediation (0.63 mA cm^− 2), soil pH developed from pH 3.5 near the anode to pH 10.8 near the cathode. The soil pH change by electrokinetics reduced microbial cell number and microbial diversity. Especially the number of culturable bacteria decreased significantly and only Bacillus and strains in Bacillales were found as culturable bacteria. The use of EDTA as an electrolyte seemed to have detrimental effects on the soil microbial activity, particularly in the soil near the cathode. On the other hand, the soil dehydrogenase activity was enhanced close to the anode and the analysis of microbial community structure showed the increase of several microbial populations after electrokinetics. It is thought that the main causes of changes in microbial activities were soil pH and direct electric current. The results described here suggest that the application of electrokinetics can be a promising soil remediation technology if soil parameters, electric current, and electrolyte are suitably controlled based on the understanding of interaction between electrokinetics, contaminants, and indigenous microbial community.     

O3／BAC工艺中溴酸盐的控制

通过试验考察了活性炭、陶粒以及挂膜陶粒对溴酸盐的去除效果,分析了微生物对溴酸盐的降解作用。结果表明,在滤池以及生物活性炭滤池内成熟的微生物膜对溴酸盐有降解能力,溴酸盐去除量与水力接触时间的关系为9．16μg（L·h）。在活性炭（GAC）吸附以及微生物降解协同作用下,可以在不增加运行成本的基础上稳定、有效地控制溴酸盐。     

Removal of metribuzin by sulfate radical‐based photooxidation: multi‐objective optimization by central composite design

The objective of this study was to optimize the experimental conditions for maximum removal efficiency and minimum operating cost for removal of metribuzin pesticide from aqueous solution. Central Composite Design model was applied as Response Surface Design. In the model, independent parameters were ultraviolet irradiation time, persulfate anion dosage, TiO₂ dosage, pH and response parameters were metribuzin removal (%) and operation cost. Analysis of variance (ANOVA) was used to describe the significance level of factors on the multiple performance characteristics considered. It has been found that the most suitable model is the quadratic model to explain the both responses and the correlation coefficient (R²) of the relationship between the actual metribuzin removal and the predicted removal was calculated as 0.9518. As a result of multi‐optimization, removal efficiency of 84.59 (%) and operation cost of 4.44 (€/g) were obtained at ultraviolet irradiation time at 12.03 min, persulfate anion concentration at 4.909 g/L, TiO₂ concentration at 0.197 g/L and pH at 4.     

Role of cell surface components on Cu2+ adsorption by Pseudomonas putida 5-x isolated from electroplating effluent

A gram-negative bacterium Pseudomonas putida 5-x with high Cu2+ accumulating capability was isolated from electroplating effluent in Kwun Tong, Hong Kong. The pretreated cells without superficial layer-capsule, isolated cell envelopes and the separated peptidoglycan layer materials were obtained from fresh P. putida 5-x cells, their Cu2+ adsorption capacities and properties were compared with that of the fresh cells. Pretreatment by 0.1 mol L(-1) HCl enhanced Cu2+ adsorption capacity due to the degradation of cell superficial layer-capsule of P. putida 5-x cells. Isolated cell envelopes possessed five times more Cu2+ adsorption capacity than that of fresh intact cell. The Cu2+ adsorption of separated peptidoglycan layer materials indicated that the peptidoglycan layer only played 10-15% part of the Cu2+ adsorption capacity, and implied other cell surface components such as outer membrane or inner membrane might play an important role in such high Cu2+ binding of the cell envelopes. The adsorption process of fresh cells, pretreated cells and cell envelopes of P. putida 5-x could be described with Freundlich isotherm, while the adsorption of Cu2+ by separated peptidoglycan layer materials was better described with Langmuir isotherm.     

Evaluation of natural and enhanced PCP biodegradation at a former pesticide manufacturing plant

Pentachlorophenol (PCP) has been used in the past as a pesticide, herbicide, antifungal agent, bactericide, and wood preservative. Thus, PCP is among the most ubiquitous chlorinated compounds found in groundwater contamination. A former pesticide manufacturing plant located in southern Taiwan has been identified as a PCP spill site. In this study, groundwater samples collected from the PCP site were analyzed to assess the occurrence of natural PCP biodegradation. Microcosm experiments were conducted to (1) evaluate the feasibility of biodegrading PCP by indigenous microbial consortia under aerobic and cometabolic conditions, and (2) determine the potential of enhancing PCP biodegradation using cane molasses and biological sludge cake as the substitute primary substrates under cometabolic conditions. The inocula used in this microcosm study were aquifer sediments collected from the PCP site and activated sludges collected from the municipal and industrial wastewater treatment plants. Results from this field investigation indicate that the natural biodegradation of PCP is occurring and causing the decrease in PCP concentration. Microcosm results show that the indigenous microorganisms can biodegrade PCP under both aerobic and aerobic cometabolism conditions. A PCP-degrading bacterium was isolated from the collected aquifer sediments and identified as Pseudomonas mendocina NSYSU via some biochemical tests and further conformation of DNA sequencing. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy. The isolated bacterium, P. mendocina NSYSU, was capable of completely degrading PCP as indicated by the increase in biomass formation with the decrease in PCP concentrations occurred in the carbon-free medium simultaneously. Results indicate that the in situ or on-site aerobic bioremediation using indigenous microorganisms or inoculated bacteria would be a feasible technology to clean up the studied PCP-contaminated site. Results from this study will be useful in designing a scale-up in situ or on-site PCP bioremediation system (e.g., on-site bioreactor) for field application.     

Ecotoxicological assessment of doxycycline in aged pig manure using multispecies soil systems

This paper assesses the ecotoxicity of the antibiotic doxycycline in aged spiked pig manure using a multispecies soil system (MS 3) covering plants, earthworms and soil microorganisms. The study reproduced realistic exposure conditions, as well as higher exposure doses covering the uncertainty factors typically employed for covering interspecies variability. MS 3, consisting of columns of natural sieved soil assembled with earthworms and seeds from three plant species, were employed. Pig manure was spiked with doxycycline (75 or 7500 microg/ml), aged for 15 days under aerobic/anaerobic conditions and added on top of the soil columns (120 ml/column, equivalent to 220 kgN/ha). Water and doxycycline free manure were used as negative controls. Doxycycline (7500 microg/ml) solution was used as a positive control. No effects on plants or earthworms were observed. Significant effects on soil phosphatase activity, indicating effects on soil microorganisms, were observed at the highest exposure dose, affecting all soil layers in the doxycycline-solution-treated MS 3 (positive control) but only the top layer in the spiked pig manure system. Chemical analysis confirmed the different behavior of doxycycline in both systems (with and without manure) and those effects were observed in soil with measured concentrations over 1 mg/kg soil. The detection of doxycycline in leachates revealed a potential mobility. Leachate concentrations were similar for doxycycline solution and spiked manure treatments.     

Bioremediation of soil contaminated with alkyllead compounds

Sandy soil, which was highly contaminated with alkyllead compounds, was taken from bore cores from a site of a former tetraalkyllead producing company. It was analyzed for its capacity to chemically and/or biologically degrade alkyllead contaminants. For this purpose, soil samples were supplied with oxygen or oxygen + minerals at different water saturation. For long-term elution, contaminated soil was packed into glass columns of 1.5m length and 10cm diameter. Oxygen-saturated water was recirculated in an upflow mode. Within a time span of 260 days tetraethyllead was completely eluted from the sandy soil and was apparently converted to triethyllead by chemical or microbiological reaction. The triethyllead concentration in the circulating water accounted for 60-80% of the maximal amount, that could be formed from tetraethyllead by a single dealkylation. This indicated that between 20-40% of the triethyllead were apparently further degraded. Only very little diethyllead accumulated in the water. The triethyllead concentration in the circulating water was highly toxic for non-adapted microorganisms. However, if a readily degradable carbon source was added, fast growth of indigenous soil bacteria was observed, but only little alkyllead degradation occurred.     

Elimination of organophosphate ester flame retardants and plasticizers in drinking water purification

Organophosphate ester flame retardants and plasticizers like tris-(2-chloro-, 1-methyl-ethyl)phosphate (TCPP), tris-(2-chloro-, 1-chloromethyl-ethyl)phosphate (TDCP), tris-(2-chloroethyl)phosphate (TCEP), tributylphosphates, triphenylphosphate (TPP), ethylhexyldiphenylphosphate (EHDPP) and tris-(butoxyethyl)phosphate (TBEP) have been studied in diverse processes for drinking water purification. The elimination efficiency of these different treatment processes, e.g., biological active slow underground passage, soil passage and technical treatment processes such as ozonization or multilayer and activated carbon filtration have been studied in three waterworks in the catchment area of the river Ruhr. In the untreated surface water the concentrations of the chlorinated organophosphates ranged 50-150 ng L(-1) TCPP, 10-130 ng L(-1) TCEP and 10-40 ng L(-1) TDCP. The amounts of the non-chlorinated alkylphosphates were in the same order of magnitude (40 ng L(-1) of the tributylphosphates, 170 ng L(-1) of TBEP and 10 ng L(-1) TPP) depending on weather and water flow. EHDPP was detected in the range of 1 ng L(-1). After the drinking water purification process in all waterworks in this study, the concentrations of the selected substances were below the respective limit of quantification (0.3-3 ng L(-1)). While activated carbon filtration as well as extended passage through soil (10-15 days residence time) were effective in eliminating all selected compounds, ozonization and multilayer filtration did not contribute to the elimination of the chlorinated compounds. The elimination effect of slow underground passage combined with soil passage concerning the halogenated compounds seemed to depend on the hydraulic residence time.     

Isolation and characterization of bacterial strains capable of growing on malathion and fenitrothion and the use of date syrup as an additional substrate

Four bacterial strains capable of growing on two organophosphorus pesticides (malathion and fenitrothion) were isolated from activated sludge. Among these isolates, the species Stenotrophomonas maltophilia was found to be capable of using fenitrothion as the sole carbon and nitrogen source, and malathion as the sole carbon source. There appear to be no similar reported findings. A crude juice of dates was tested as an additional carbon source for malathion degradation. The biodegradability was significantly enhanced with the supplementation of date juice. The degradation efficiency of the pesticide tested at a concentration of 60 mg/L reached the maximum value of 89% in the presence of date juice at 30 g/L reducing sugar. Statistical screening of four operating parameters (initial biomass concentration, aeration rate, agitation and temperature) for biomass growth and for malathion degradation by acclimated indigenous activated sludge was carried out using a fractional factorial design.     

Occurrence and fate of the antidiabetic drug metformin and its metabolite guanylurea in the environment and during drinking water treatment

Metformin, an antidiabetic drug with one of the highest consumption rates of all pharmaceuticals worldwide, is biologically degraded to guanylurea in wastewater treatment plants. Due to high metformin influent concentrations of up to 100 μg/L and its high but incomplete degradation both compounds are released in considerable amounts of up to several tens of μg/L into recipient rivers. This is the first systematic study on their environmental fate and the effectiveness of treatment techniques applied in waterworks to remove metformin and guanylurea from surface water influenced raw waters. The concentrations in surface waters depend strongly on the respective wastewater burden of rivers and creeks and are typically in the range of about 1 μg/L for metformin and several μg/L for guanylurea but can reach elevated average concentrations of more than 3 and 20 μg/L, respectively. Treatment techniques applied in waterworks were investigated by an extended monitoring program in three facilities and accompanied by laboratory-scale batch tests. Flocculation and activated carbon filtration proved to be ineffective for removal of metformin and guanylurea. During ozonation and chlorination experiments with waterworks-relevant ozone and chlorine doses they were partly transformed to yet unknown compounds. The effectiveness of the treatment steps under investigation can be ordered chlorination > ozonation > activated carbon filtration > flocculation. However, most effective for removal of both compounds at the three full-scale waterworks studied proved to be an underground passage (riverbank filtration or artificial groundwater recharge). A biological degradation is most likely as sorption can be neglected. This is based on laboratory batch tests conducted with three different soil materials according to OECD guideline 106. Since such treatment steps were implemented in all three drinking water treatment plants, even traces of metformin and its metabolite guanylurea could not be detected at the end of the treatment trains. Both can only be expected in finished drinking water if surface influenced raw water is used by direct abstraction without underground passage.     

Promotion and inhibition of oxygen transfer under fine bubble aeration by activated sludge

The promotion and inhibition of inactivated and activated sludge on oxygen mass transfer (OMT) were studied using lab‐scale experiments. The results showed that the α‐values and oxygen transfer efficiency (OTE) decreased with increasing mixed liquor suspended solids (MLSS) concentration (1–10 g/L). Although OMT promotion rate by microbial respiration in activated sludge system increased from 39.8–97.5% for the α‐values and OTE, the two parameters were found to fall sharply when MLSS concentration was over 5 g/L. This indicated that the sludge concentration is a major influence factor on OMT in activated sludge system. Such results provide valuable knowledge for the operating optimization of the aeration system in wastewater treatment process.     

联氨对HABR全程自养脱氮系统的影响

为考察联氨作为自养脱氮系统菌群调节剂的可行性,以实验室内运行的HABRCANON反应器为试验装置,研究不同浓度联氨对自养脱氮系统脱氮效能和功能微生物的影响。结果表明,低浓度(1~4 mg/L)联氨可以抑制亚硝酸盐氧化菌(NOB)的活性,促进厌氧氨氧化菌(AnAOB)的活性,从而提高脱氮效能;高浓度(10 mg/L)联氨对好氧氨氧化菌(AOB)和NOB的抑制作用明显;停止投加联氨后,CANON系统的脱氮效能可迅速恢复;高浓度(10 mg/L)联氨对HABR全程自养脱氮工艺的影响是可逆的,但对NOB的抑制不可逆。对生物膜样品中的优势菌种进行分析发现,AOB和AnAOB为主要的功能微生物。采用低-高-低的联氨投加方式,可以有效抑制自养脱氮反应器内NOB的生长,保证自养脱氮系统的稳定运行。